Increasing Hydraulic pressure on Deere 790

[raamw]

I have a 2006 790 with a 300FEL, the lifting power on the loader is less then what I would like. I have heard a simple shim kit is all I need to remedy this any idea what these costs and where I can finds it plus what is the procedure to install


Thanks in advance for any insight

 

[kebo]

There have been several threads on this, here are three of them. I did mine, very easy. You will need a 0-3000 (preferred) or 0-5000 psi filled gauge to measure the before/after pressures. I used a full shim kit, and a thin shim from a second kit to get mine dead on 2500psi. Guage was $28 with a couple fittings, and the two shim kits were about $18 I think. Good luck!

http://www.tractorbynet.com/forums/...ing/49539-790-raising-hydraulic-pressure.html

http://www.tractorbynet.com/forums/john-deere-owning-operating/129457-jd-790-300-loader.html

http://www.tractorbynet.com/forums/john-deere-buying-pricing/119041-jd-790-4x4.html#post1371558

 

[J_J]

I have a 2006 790 with a 300FEL, the lifting power on the loader is less then what I would like. I have heard a simple shim kit is all I need to remedy this any idea what these costs and where I can finds it plus what is the procedure to install


Thanks in advance for any insight

You should know or find out what the working pressure is for your tractor. You should get a gage anyway for all test, and install tee fittings at critical points. To test the pump pressure, you need to put a needle valve in the circuit to put a load on the pump circuit. To set this up, add a tee to the hose going to the first valve, then a needle valve, and connect the other side of the needle valve to the control valve. Never close the needle valve all the way, or the pump maybe damaged.

To test pump, open the needle valve all the way open. Start and run the tractor at rated rpm. Turn the needle valve in until the pressure builds up to pump running pressure. Make a note of this pressure.

To test the relief, open the needle valve all the way, and activate one of the cylinders on the control valve, and hold the control lever until the cylinder extends all the way. You should hear the relief valve going off, and see the pressure that it is relieving.

Now assuming that the pump is good, and the control valve is good, then you can adjust the relief pressure , keeping it below the running pump pressure, by using the shims. About 200 to 300 psi below pump pressure.

If it does not relieve, that means that the relief valve is not working, maybe leaking, or the cylinder is bypassing, and the system can never achieve the useful pressure of the pump.

If the pump output is ever blocked or dead-headed, something is going to break.

The pump below is an example . Max psi of 3000, but the rated GPM is at 2500 psi.


https://www.surpluscenter.com/item.asp?UID=2009072417472278&item=9-4437-B&catname=hydraulic

 

[kennyd]

You should know or find out what the working pressure is for your tractor. You should get a gage anyway for all test, and install tee fittings at critical points. To test the pump pressure, you need to put a needle valve in the circuit to put a load on the pump circuit. To set this up, add a tee to the hose going to the first valve, then a needle valve, and connect the other side of the needle valve to the control valve. Never close the needle valve all the way, or the pump maybe damaged.

To test pump, open the needle valve all the way open. Start and run the tractor at rated rpm. Turn the needle valve in until the pressure builds up to pump running pressure. Make a note of this pressure.

To test the relief, open the needle valve all the way, and activate one of the cylinders on the control valve, and hold the control lever until the cylinder extends all the way. You should hear the relief valve going off, and see the pressure that it is relieving.

Now assuming that the pump is good, and the control valve is good, then you can adjust the relief pressure , keeping it below the running pump pressure, by using the shims. About 200 to 300 psi below pump pressure.

If it does not relieve, that means that the relief valve is not working, maybe leaking, or the cylinder is bypassing, and the system can never achieve the useful pressure of the pump.

If the pump output is ever blocked or dead-headed, something is going to break.

The pump below is an example . Max psi of 3000, but the rated GPM is at 2500 psi.


https://www.surpluscenter.com/item.asp?UID=2009072417472278&item=9-4437-B&catname=hydraulic

JJ, with all due respect...you are make this way to complicated! All those Tee's and a needle valve? He just needs to plug the gauge into one of the loader ports as described in the three threads that where referenced to him. This is a very common procedure on the 790's.

 

[J_J]

I understand what your are saying, but the instructions above were based on the fact, that he might not know the working pressure. He never said whether the valve was going into relief, and if he has other troubles than the relief, he might have other troubles.

 

[raamw]

The tractor is basically new with 37 hours, it seems to be lacking shovel power, I get stuck in the mud quite often and I need the FEL to back me out, it normally works but not as well as it could, if I get the rear wheels in deep I know it won't work